Production of butadiene



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PRODUCTION O BUTADIENE Filed .July 29, 1943 IAII lAnII Patented'Apr. 24,19.45

:miras STATES. PATENT ortica Clayton S. Wynn, Darien, Conn., assignor toAir Reduction Company, Incorporated, New York, N. Y., a corporation o!New York Application July 29, 1943, SerlallNo. 496.556

1 Claim.

This invention relates to the production of 1,3- butadiene lfrom1,3-butylene glycol and particularly to improvements in the recovery andutilization of partially reacted glycol or butenol from the condensateafter separation of butadiene.

1,3-butadiene is derived from 1,3butylenc glycol by splitting oi waterin accordance with the following reaction:

CI'l's--CHOH-CH's-CHaOH-r CHa==CH-CH=CH2+ 21H20 In both of theprocedures described in the applications mentioned, vapor includingbutadiene and other products is removed Afrom the reactor. Uponcondensation, butadiene is withdrawn as a vapor. The condensate includesa considerable quantity of partially reacted glycol or butenol. It is,however, contaminated by materials, of an oily character andundetermined composition, which if returned to the catalyst may causerapid deterioration and loss of activity.

It is the object of the present invention to prol vide a simple andsatisfactory procedure whereby the contaminating materials may beseparated readily from the butenol which is recovered for further use inthe reaction.

Other objects and advantages of the invention reference to the followingspeciilcation and the accompanying drawing, which illustratesdiagrammatlcally an apparatus suitable for the practice of theinvention.

For the purpose of describing the invention, reference will be made tothe details of the procedure involved in the vapor phasedehydration of1,3-butylene glycol. It is to be understood, however, that the inventiono! the present application is equally applicable to the recovery ofbutenol formed as a result of reaction of 1.3- butylene glycol in thepresence of a catalyst suspended or dissolved in a suitable liquid, asdescribed in the earlier of the Lorch applications.

Butadiene can be produced advantageously by passing 1,3-butylene glycolin the vapor phase over a catalyst mass which is adapted to with- Awillbe apparent as it is better understood by Y reaction.

stand the disintegrating effect o! free phosphoric acid. vThe catalystmass is maintained preferably at a temperature ranging from 220 to 400C., the most eilective range for the catalyst hereinafter describedbeing approximately 280 to 320"l C. The temperature may be maintained bycirculating a suitable heating medium such, for example, as a mixture ofdiphenyl and diphenyl oxide known as "Dowtherm about the catalyst body.

As the catalyst, I prefer to employ "ammonium phosphate." Theterm"ammonlum phosphate-' is'yemployed as a general designation of thetri, di and mono ammonium phosphates or mixtures of these salts.- It isemployed also to include decomposition products` of these phosphateswhich are subject to modication when subjected to temperatures such asthose employed in the method. The precise composition of the resultantsalt or salts in the catalyst mass at the temperature maintained cannotbe determined accurately. Any of the phosphates mentioned or theresulting products are active catalysts for the Ammonlum phosphate" ismarkedly superior to the phosphate catalysts which have been mentioned.in the literature concerning dehydration of 1,3-butylene glycol.

In order to attain the most effective use of ammonium phosphate" as acatalyst for the reaction, it is desirable to mount it on a suitablesupport. Most of the supports commonly suggested for use in thepreparation of catalyst bodies are useless for the purpose of thepresent invention because they do not withstand the disintegratingeilect of free phosphoric acid which is inevitably present at thetemperature employed. Silica aiords a satisfactory support for ammoniumphosphate in catalyst masses to bel employed for the purposeofjthepresent invention. The preferred forms of silica are a calcineddiatomaceous earth consisting essentially of silica and generally knownas "Celite V. Another type of supportA is silica bonded with feldspar.lAny relatively pure silica may be frltted with the addition oi feldsparto produce a material adaptedior use as a support which porting materialand the mass may be dried while it is stirred to maintain uniformity.Whatever procedure is adopted, the supportingmaterial carrying theammonium phosphate may be formed into pellets in accordance with theusual method. The pellets may be of any desired size adapted to affordmaximum surface contact with the necessary interstices through which thevapor may readily pass.

The proportion of the ammonium phosphate" in the catalyst mass may bevaried over wide limits. It will depend in part upon the degree and typeof porosity of the supporting material as well as the size of thepieces. Satisfactory catalysts have been prepared covering the range ofto 60% ammonium phosphate. The size of the individual pieces of catalystcan be varied within wide limits to secure the optimum contact with thereactant gases.

As the result oi dehydration of the 1,3-butylenevglycol, butadiene isproduced admixed with unreacted and partially reacted glycol. By passingthe vapors through a suitable condenser at about 100 C., the unreactedglycol can be liquefied, separated and returned for further treatment.The partially reacted glycol or butenol with water and the butadienepass the condenser. These vapors are then subjected to further coolingin a second condenser and the butadiene is separated as a vapor. It maybe compressed and condensed by cooling to a liquid, or it may bewithdrawn and stored in the form of vapor.

The partially reacted glycol or butenol and water resulting from thereaction, together with some contaminating compounds, are condensed to aliquid. The contaminating compounds are insoluble in water, whereas thebutenol is soluble. To recover the butenol, the condensate is washedwith water. The oily residue which rises to the top of the washing toweris withdrawn and discarded. The water soluble butenol dissolved in`thewash water is then subjected to distillation in the rectifier 40. Therectiiler is heated at the to separate an azeotrope of butenol andwater.

The azeotrope may be condensed and returned for further dehydration andcontact with the catalyst. The separated water is withdrawn anddischarged from the bottom of the rectier.

The procedure will be readily understood by reference to the drawing,the apparatus being merely illustrative of suitable equipment for thepurpose. The reactor 5 may be a tubular chamber of suitable materialsurrounded by heating jackets 6 towhich the heating iiuid is introducedthrough a pipe 1 and withdrawn through a pipe 8.- The catalyst 9 isdisposed within the chamber 5 in the form of pellets of suitable size toeffect the desired result.

1,3-butylene glycol is supplied through a pipe l l0 to a vaporizer Ilwhich may be heated, for

example, by the passage of a suitable liquid such as Dowtherm through ajacket I2. The heating liquid is introduced through a pipe I3 andwithdrawn through a pipe I4. The glycol is thus vaporized and deliveredto the reactor 6 by a pipe i5.

The gaseous products of the vreaction are withdrawn through a pipe I6and delivered by a condenser I1 supplied with a cooling liquid such aswater through a pipe I8. The water escapes through a pipe I9. Thecondensate, consisting of unreacted glycol. is delivered by a pipe 20 tothe pipe l0 and vaporizer Il.

The remaining vapors are delivered by a pipe 2l to a condenser 22through which a cooling liquid such as water is circulated by pipes 23and 24. The condensate is delivered to a collector 25. Butadiene escapesthrough a pipe 26 and is preferably compressed by a compressor 21 beforeit enters a condenser 28. Cooling water may be introduced through a pipe29 and withdrawn through a pipe 30. The butadiene in the liquid phasemay be withdrawn through a pipe 3l and delivered to a suitable storagereceptacle.

The condensate in the collector 25 is delivered through a pipe 32controlled by a valve 33 to a washing tower 34 which may be filled withany suitable packing material such as rings or other devices tofacilitate contact between the condensate rising through the tower andwater which is introduced at the top through a pipe 35. As a result ofthe washing action, the water soluble butenol is separated from thecondensate. An oily layer including contaminating compounds rises to thetop and is withdrawn through a pipe 36 controlled by a valve 31.

The wash water, with the dissolved butenol, escapes through a pipe 38and is delivered by a pump 39 to a rectiiier 40 which may be providedwith the usual bubble caps 4| or other means for facilitating contactbetween the liquid and vapors bottom by means of a steam coil 42. Theresulting vapors rising through the rectiiier form an azeotrope ofbutenol and water which escapes at the top through a pipe 43. Water maybe withdrawn from the bottom of the rectifier through a pipe 44controlled by a valve 45.

The azeotrope of butenol is delivered by the pipe 43 to a condenser 46which may be cooled with water introduced through the pipe 41 andwithdrawn through the pipe 48. The condensed azeotrope is deliveredthrough a pipe 43 and pump 50 to the pipe I0 and is thus returned forvaporization and introduction with the glycol to the reactor 5.

The partially reacted glycol or butenol is thus freed from impuritieswhich, if retained, might aiiectthe catalyst or otherwise interfere withthe dehydration reaction. Butenol is readily dehydrated in contact withthe catalyst to produce butadiene. Hence the eillciency of the operationis improved by the procedure hereinbefore described.

Various changes'may be made in the apparatus employed and in the detailsof the procedure without departing from the invention or sacrincing theadvantages thereof.

I claim:

The method oi dehydrating 1,3-butylene glycol.

CLAYTON B. WYNN.

